32 
SEXUAL SELECTION. 
Part II. 
thought dangerous by their enemies. The cause, how- 
ever, of the bright colours of the venomous Elaps 
remains to be explained, and this may perhaps be 
sexual selection. 
Lacertilia . — The males of some, probably of many 
kinds of lizards fight together from rivalry. Thus the 
arboreal Anolis cristatellus of S. America is extremely 
pugnacious : During the spring and early part of the 
“ summer, two adult males rarely meet without a con- 
test. On first seeing one another, they nod their heads 
up and down three or four times, at the same time 
expanding the frill or pouch beneath the throat ; their 
eyes glisten with rage, and after waving their tails 
from side to side for a few seconds, as if to gather 
energy, they dart at each other furiously, rolling over 
and over, and holding firmly with their teeth. The 
conflict generally ends in one of the combatants losing 
his tail, which is often devoured by the victor.” The 
male of this species is considerably larger than the fe- 
male and this, as far as Dr. Gunther has been able to 
ascertain, is the general rule with lizards of all kinds. 
The sexes often differ greatly in various externa 
characters. The male of the above-mentioned Anolis 
is furnished with a crest, which runs along the back and 
tail, and can be erected at pleasure ; but of this crest 
the female does not exhibit a trace. In the Indian 
Gopliotis ceylaniea^ the female possesses a dorsal crest, 
though much less developed than in the male ; and 
so it is, as Dr. Gunther informs me, with the females 
of many Iguanas, Chamelions and other lizards. In 
some species, however, the crest is equally developed in 
both sexes, as in the Iguana tulerculata. In the genus 
Mr. N. L. Ansten kept these animals alive for a considerable time 
see ‘ Land and Water,’ July, 1867, p. 9. 
